Motion converter

ABSTRACT

This invention relates to a motion converter for converting the oscillating movement of a mechanical vibrator. The motion converter according to this invention is characterized by that the feed pawl is designed to have a substantial resiliency in its oscillating direction and the ratchet wheel has a substantial moment of inertia, said pawl resiliency and said ratchet inertia serving in combination for converting otherwise stepwise intermittent movement of said ratchet wheel into a substantially continuous and constant rotation thereof.

United States Patent [1 1 Kato et al.

[451 Dec. 25, 1973 MOTION CONVERTER [76] Inventors: Yoshiaki Kato, 20-46, 4-chome,

Higiyama-cho, Higashimuraya-shi, Tokyo; Hiroshi Mabuchi, 873, Shimotomi Takeno, Tokorozawa-shi, both of Japan 22 Filed: July 14, 1971 [21] Appl. No.: 162,360

[30] Foreign Application Priority Data May 26, 1971 Japan 46-3608] [52] US. Cl. 58/23 D, 58/23 V,- 58/23 TF, 74/128 [51] Int. Cl....L G04c 3/00 [58] Field or Search; 58/23 R, 23 TF, 23 D, 58/23 v; 74/128, 142

[56] References Cited UNITED STATES PATENTS 2,90 ,174 10 1959 Hetzel 74/128 Hetzel 58/23 TF Steiger 58/23 V Primary Examiner-Stephen J. Tomsky Assistant ExaminerEdith Simmons Jackmon Attorney-Richard C. Sughrue et al.

57 ABSTRACT This invention relates to a motion converter for converting the oscillating movement of a mechanical vibrator.

The motion converter according to this invention is characterized by that thefeed pawl is designed to have a substantial resiliency in its oscillating direction and the ratchet wheel has a substantial moment of inertia, said pawl resiliency and saidratchet inertia serving in combination for converting otherwise stepwise intermittent movement of said ratchet wheel into a substantially continuousand constant rotation thereof.

5 Claims, Drawing Figures PATENIEU DEC 25 I975 SHEET 2 (IF 3 PAIENIEDmzs ma 3. 780 5 l 8 sum 30F 3 1 MOTION. CONVERTER This invention relates to a motion converter mechanism for converting the oscillating movement of a mechanical vibrator into a corresponding rotary movement of a ratchet wheel and especially adaptedfor use in the electronic timepiece, preferably a watch.

Conventional motion converters of the above kind are generally so designed that there are provided a pair of pawls, one being called feed pawl and the other being called stop pawl, of which the feed pawl is fitted to the mechanical vibrator and kept in meshing with. a ratchet wheel so as to perform unitary oscillations with the vibrator for driving the ratchet correspondingly, said stop pawl being also kept in meshing with the ratchet and serving for checking otherwise possible reverse rotation thereof in. the course of said driving. It will be seen from the foregoing that such ratchet drive is carried out effect only in an intermittent way. Although such ratchet drives have been already disclosed in various prior specifications, we would like to refer as a representative thereof to US. Pat. No. 3,184,923]

which discloses such a mechanism that a tuning fork is used as the mechanical vibrator and the feed pawl is pivotably attached thereto and operatively connected with an index wheel for driving the latter.

Such conventional ratchet mechanisms represent, however, the following various drawbacks.

At first, it should be pointed out, asalready referredto in said U.S. Patent specification, that in orderto accurately transmit the oscillative movements from the mechanical vibrator to. the ratchet wheel, feed pawl and stop pawl must have a correct mutual distance corresponding to a certain plurality of tooth pitches of the ratchet plus just a half thereof whenmeasured at the engaging points of these pawls with the ratchet. This. requirement must be fulfilled as far as possible which results in a highly troublesome and time-consuming adjusting job when watch movement parts are being assembled together. When the requiredpositional requirements has once been established, a slight outside shock will change it into an offset relationship from the prescribed one. When such trouble should occur, the regular working of the watch movement is naturally disturbed considerably.

Secondly, especially when both the feed and stop pawls are arranged substantially in a parallel and relatively close mutual relationship, and when the ratchet wheel is mounted in a slightly eccentric position. deviating from the true and correct concentric position, as may be frequently encountered in practice byvirtue of unavoidable mechanical errors in workmanship, the. mutual distance between the both pawls will fluctuate for every revolution of theratchet, thereby inviting periodical deviations in their working position relative to each other and disturbing the desired dynamic balance in the mean and regular stepped mode of the watch movement. As ascertained by our practical experiments, the practically allowable eccentricity in the mounting of the ratchet wheel should be within only a small part of a tooth pitch. Therefore, high precision machining and mounting of the ratchet is required, especially when the timepiece is of small caliber. The realization of these requirement can be made only with substantial difficulty and at a highly reduced manufacturing efficiency. A substantial increase of the number of the ratchet teeth necessary for obtaining a more optimum conversion so as to rotate the ratchet at a slower revolutional speed has been prevented from its practical realization from the same reason as set forth above.

In order to realize a' smoother and efficient ratchet type motion converter, it is highly desirable to perform the motion convertion substantially in a continuous way, in place of conventionally employed intermittent mode. In addition, an abolition of the stop pawl is also highly desirous so as to simplify the assembly job of the motion converter.

The main object of the present invention is to provide an improved motion converter, capable of substantially obviating the aforementioned conventional drawbacks.

This and further objects, features and advantages of the invention will become more apparent when read the following detailed description of the invention by reference to the accompanying drawing;

In the drawings:

FIG. 1 is a schematic front view of essential parts of a first embodiment of the motion converter constructed according to the present invention,

FIGS. 2 and 3 are two explanatory schematic views for-the illustration of the working mode of the motion converter shown in FIG. 1;

FIG. 4 is a plan view of a second embodiment of the motion converter, partially sectioned and broken away and partially shown in a highly simplified schematic way;

FIGS. 5a-5f shows several embodiments in their respective perspective views of the feed pawl employable in' the motion converter; and

FIG. 6 is an explanatory chart, illustrating the stabilized working condition of the motion converter.

Referring now to FIG. 1, numeral 1 represents schematically a conventional mechanical vibrator, preferably in the form of a tuning lead, an arm of tuning fork,

or similar oscillatory member, which is adapted for performing oscillation on the plane of the drawing paper, as-shown schematically by a double headed arrow. Numeral 2 generally denotes a feed pawl, preferably in the form of a spring strip, the root end of which is rigidly attached, by hammering, press-fitting similar conventional fixing means, to a positioner 3 preferably formed into a headed and slotted pin, and angularly adjustably mounted in a corresponding opening formed in the vibrator 1, while the opposite or actuating end of said pawl has a pallet stone 2a rigidly mounted thereon and kept in meshing with ratchet teeth 4a formed on a ratchet wheel 4. The root portion of the vibrator l is securely mounted on a stationary member 100, preferably a conventional plate of the watch movement.

A flywheel 5 is concentrically attached to the ratchet wheel 4, and the thus formed wheel assembly is further attached rigidly and concentrically with a pinion 6, and rotatably mounted on a stationary supporting member, such as bridge or the like, by a common shaft, although not shown specifically on the drawing.

An intermediate part 2b between the root and actuating ends of the feed pawl 2, is formed into substantially an S-shape or a similar wavy shape, so as to present substantial resiliency or elasticity in the axial or vibrating direction of the feed pawl. In addition, the feed pawl 2 is kept in engagement at its actuating end with ratchet teeth 4a by a slight radially-directing resilient or spring pressure.

Pinion 6 meshes with an intermediate gear 7 which is fitted rigidly with a pinion 8, said gear 7 and pinion 8 consituting in combination an intermediate wheel assembly which is rotatably mounted on the aforementioned bridge, although not shown.

Pinion 8 meshes with conventional seconds wheel 9 which carries a seconds hand 10 as schematically shown. Gears and pinions 6 9 constitute a substantial part of the conventional time-keeping and indicating gear train of the watch movement.

In the following, the operation of the first embodiprising the ratchet wheel 4 and all related rotational members through second hand 10, is selected to be sufficiently large, so as to maintain a practically constant rotational speed when driven as will be more fully described hereinafter, inspite of the very presence of the oscillatory driving force exerted thereupon by the feed pawl 2, the load imposed on the rotatable assembly, the friction loss mainly appearing between pallet stone 2a and the rear tooth surface of ratchet 4, the reversed or dragging force acting between said stone and said surface appearing in course of the receding stroke of said pawl 2, and so on. More specifically, the inertia corresponds to the ratio of the kinetic energy of the rotational system including ratchet 4 and similar rotational members referred to above, multiplied by the integer: 2 and divided by a square of the peripheral speed of ratchet 4, said inertia having thus the dimensions of mass."

2. The mass of feed pawl'2 has been selected sufficiently small so as to be neglected in comparison with the said inertia.

3. The root or fixed end of feed pawl 2 describes a sinusoidal movement if plotted against a time-indicating axis, and at a constant frequency equal to that of the mechanical vibrator l, irrespective the disturbing reaction force inversely transmitted from the side of pallet stone 2a through the body of pawl 2 to the root end thereof.

4. When the apllet stone 2a slides along the inclined rear tooth surface of the ratchet tooth 4a, the axial displacement of the pallet is equal to that of the root end of feed pawl 2, irrespective 'of frictional resistance acting between the pallet and the inclined rear tooth surface on ratchet 4.

Next, referring to FIGS. 2 and 3, the meaning and mutual relationship between the oscillative movement of mechanical vibratior 1, that of the pallet stone 2a and that of ratchet teeth 4a will be described below in detail. In FIG. 2, the arrowed horizontal axis represents the displacement of the root end of feed pawl 2 and that of each of several ratchet teeth, while the arrowed vertical axis, t, represents the progress of time. FIG. 3 shows schematically and on a substantiallyenlarged scale a portion of FIG. I.

In FIGS. 2 and 3, pallet stone 2a is about to start to perform an actuating stroke together with its supporting feed pawl 2 at the intersection point of the both axes or origin 0. This starting position of pallet stone 2a is also clearly shown in FIG. 3. This receded position of the pallet stone is shown at P in FIG. 2.

With oscillatory movement of mechanical vibrator 1 under these conditions, pallet stone 2a will slide from said point P along the inclined rear tooth surface (N l)" of (N 1)th ratchet tooth in the advancing or actuating direction towards the motion-receiving or front tooth surface N of Nth ratch tooth at a rather quicker displacement speed than that of the related ratchet tooth, until it strikes against the said front tooth surface, along the curve portion P P,. The time point where such striking or collision is brought about is shown at t, on the chart in FIG. 2. With further advancing or ratchet-driving movement of pallet stone 2a for a time period (t, t accompanying the tooth N for rotational driving of the ratchet, a substantial amount of elastic energy is being stored in the resilient portion 2b of pawl 2. Durin this energy storing and elastically driving period (t, t the root end of pawl 2 will describe a curved portion (P, P on the said sinusoidal curve in FIG. 2, while pallet stone 2a describes a straight line portion (P P appearing on the same figure.

It should be mentioned that the resiliently stored energy in the resilient portion 2b can be expressed by the shadowed area S,,." At the point P corresponding to time point t the provisionally and resiliently stored energy has all been dissipated for elastic drive of the ratchet 4. During further time period (t, l/f), f being the oscillating frequency of vibrator 1, corresponding to a point P pallet stone 2a will recede from driving contact with the front tooth surface N and ride over the (N l)th tooth onto the next following (N 2)th tooth, and so on. During this final stage period of one cycle of the oscillatory movement of vibrator 1, the root end of the feed pawl 2, as well as the pallet stone, will describe a curved portion P P P, in FIG. 2. In this way, a complete oscillation cycle has been accomplished at the time point P, or (l/f).

In order to analyze the aforementioned oscillating driving movement of the pallet stone through the axially resilient feed pawl, the following nomenclature is adopted:

X horizontal distance between motion-receiving or front tooth surface of tooth N and the outer end surface of pallet stone 2a;

X horizontal displacement of root end of feed pawl 2;

X horizontal displacement of front tooth surface of tooth N;

. pitch of ratchet wheel 4a;

. spring constantof feed pawl 2 as measured in the axial direction thereof;

. oscillation frequency of vibrator;

semi-amplitude as measured at the root end of feed pawl;

n number of ratchet teeth passing through the tip and bottom corner of pallet stone during performing a complete oscillation cycle;

v advancing velocity of ratchet tooth measured in circumferential direction of ratchet wheel;

X initial phase distance of pallet stone, as measured when the pallet is positioned at its most receded position and between motion-receiving front surface of ratchet tooth and the front tip end of said pallet;

t time ordinate as measured from origin set at the most receded point of pallet before driving contact thereof with front or motion-receiving surface of Nth ratchet tooth;

t, time point where drive contact of pallet with ratchet tooth N begins;

t time point where drive contact of pallet with ratchet tooth N has been interrupted;

F force acting between pallet and front or motion-receiving surface of ratchet tooth;

W total sum of -,drive energy transmitted from pallet to ratchet wheel during a complete oscillation cycle;

W total sum ofenergy dissipated by ratchet wheel assembly during a complete oscillation cycle for maintaining the continuous revolution thereof;

S shadowed area appearing in FIG. 2, having a dimension of length multiplied by time;

From the foregoing, we obtained:

v n f P (2) X2 X V t =Xo+n'f'P't (3) Thus,

X may be of negative value. In this case, a compressive force acts between the front surface of pallet and the front tooth surface N, thus the resilient portion 2b being subjected to compression. Therefore, a drive force will act upon the tooth N. The drive energy W caused by application of this drive force F will be 2 l, W1) 'F 1) dt '1 =K'n'P'f'Sn Therefore, the conditions necessary for performing a stabilized feed of ratchet will be 1. presence of period in which driving force can be generated mtn 0 2. The amount of work exerted by said drive force upon the ratchet wheel assembly must be in balance with the total sum of energy dissipated by the assembly. Or in other words It will be seen from the foregoing that so far as the various operating conditions above referred to are within respective regular ranges, the motion converter can perform a steady operation. But, even under certain irregular and deviated operating conditions as will be analysed hereinunder, the converter may perform its destined job.

I. In case of fluctuated load condition When it is assumed that, as an example, the load becomes a substantially large value W,,' from W then can be maintained to a modified steadily operating condition. In this way, a newly established steady rotation of the ratchet wheel assembly will be maintained without difi'iculty.

Orconversely, with reduced load, the operational phenomenon will be reversed from the foregoing. Therefore, again in this case, a steady rotational movement of the ratchet wheel assembly can be established and maintained without difficulty.

II. In case of fluctuated amplitude of mechanical vibrator As an example, when theregular amplitude of the vibrator is increased to a larger value, as may be caused by an outside disturbing cause, from A to A, the value of S will be correspondingly increased and the drive force will become larger again correspondinglvTherefore, the rotational speed of the ratchet wheel assembly will be increased correspondingly. Thus, the value of X 0 per revolution will become gradually larger, until the value of S recovers its initial one in advance of the introduction of the amplitude fluctuation and a newly achieved stabilization of the rotational movement is maintained, and vice versa.

The load or amplitude fluctuation in the above sense may be either of temporary or permanent nature, but the results could be same.

Ill. In case of start from the stopped condition of the mechanism At first, the amplitude of the mechanical vibrator will become gradually increased, and the pallet stone will perform during this initial starting period a repeated hammering action against a certain ratchet tooth with which the pallet repeatedly engages. With a substantial increase of the oscillation amplitude of the vibrator accompanying the feed pawland its actuating pallet stone and when the latter rides over the presently engaged ratchet tooth onto the neitt following one, the ratchet will receive a large amount of drive force which corresponds substantially to the overall amplitude of oscillation, whereby the ratchet is quickly and strongly accelerated. In this way, a stabilized and steady rotation of the ratchet will be realized and maintained. The rotational movement is naturally unidirectional.

Next, referring to FIG. 4, the second embodiment will be described in detail hereinbelow.

In this figure, numeral 11 represents a mechanical vibrator having two oscillatory arms 11a and 11b and a short and central fixing arm 1 1c, thus being formed into substantially a W-shaped configuration when seen in its plan view as shown. This vibrator 11 is fixedly mounted on the conventional plate 25 by means of set screws 26 and 27. Thus, vibrator 11 can be considered as a specific embodiment of the vibrator 1 in the foregoing first embodiment. The plate 25 corresponding to the foregoing stationary member 100. The oscillatory arms 11a and 11b oscillate as commonly known in the opposite phase to each other and in an imaginary plane parallel to the plate 25.

A feed pawl 12, having an elongated substantially L- shape, is pivotably attached at its root end 12b to one of the oscillatory arms at 11b as shown. Although this feed arm 12 is only schematically shown in FIG. 4, its specific configuration is demonstrated at (a) in FIG. 5. At the free or actuating end of pawl 12, a pallet stone 12a is fixedly mounted as before. The foregoing feed arm 2 together with fixedly attached pallet stone 2a is specifically shown at (b) in FIG. 5.

By virtue of the L-shape, the feed pawl 12 has a substantially large axialresiliency, in addition to a substantially smaller lateral resiliency. The pallet stone 12a is kept in meshing with .a ratchet wheel 13 which is made integral and concentrically with a larger gear-type inertia mass 15, the thus provided assembly being rotatably mounted on the plate 25. This assembly is further attached rigidly and concentrically with a pinion l4 and adapted for performing'counter clockwise rotation, as shown by a small arrow.

The term axial as used throughout this specification and appended claims does mean such direction as being defined by the both end extremities of the feed pawl.

Pinion 14 is kept in drive engagement with a gear 16 which is the first one of the conventional time-keeping and time-indicating gear train further comprising a set of gears 17 22 following said gear and kept in meshing one after another, so as to provide a conventional reduction gearing. Gear 18 can be deemed as the seconds wheel and gear 22 may be considered as the minute wheel, in the specific present embodiment. Member 23 represents a seconds hand, while a minute hand has been omitted from the drawing only for simplicity.

Gear type inertia mass 15 is formed on its outer periphery with gear teeth 15a, and a further gear type inertia mass 24 is kept in meshing therewith. Both inertia masses l and 24 have preferably the same diameter as well as same inertia and are arranged to rotate in opposite directions to eachother. As conventionally, the constituent gears of said gear train are mounted rotatably and, in effect, on the plate 25.

The provision of these inertia masses l5 and 24 will substantially and amazingly serve, by the combination of the axially resilient structure of the feed pawl 12, for minimizing otherwise substantial rotational fluctuation of the ratchet wheel 13 per revolution, so as to realize substantially a continuous revolution of the wheel 13, in place of the conventional intermittent ratchet feed movement thereof.

In the motion converter according to this invention, it is highly remarkable and astonishing that the conventionally appearing cyclic and provisional stop motion of the ratchet wheel has substantially disappeared.

In the present embodiment, the equivalent inertia of the ratchet wheel is selected so large that the rotational velocity fluctuation is limited to 25 percent or less under the steadily operating condition of the watch movement. This feature is also applicable to the foregoing first embodiment.

In the present embodiment, the related rotational members are so designed and arranged that the ratchet wheel and its related gears have a algebraic total sum of angular momentums substantially equal to nil under the steadily operational conditions of the watch movement. More specifically, the absolute value of the total sum of angular momentums of the clockwise rotating constituent gears and their equivalents is substantially equal to that concerning the counter-clockwise rotating constituent gears and their equivalents. Generally speaking, the angular momentum of gears 16 21 is substantially smaller than that of inertia wheel 15, the mating inertia wheel 24 compensating substantial part of the angular momentum thereof is so designed that it has substantially equal inertia with that of the former.

Oscillatory arms 11a and 11b carry at their top end respective yokes 30a and 30b on which are rigidly mounted respective permanent magnets 28a and 28b adapted for cooperation with stationary drive coil 29a and sensing coil 29b, respectively. As conventionally, these coils 30a and 30b are included in a drive circuit comprising transistor 31, condenser 32, resistor 33 and current source 34. Such drive circuit is commonly known and may be modified in a broad sense to take other known form and style.

When the electronic watch is kept in its regular and steady motion as conventionally, the magnets 28a and 28b, together with respective yokes 30a and 30b and oscillatory arms 11a and 11b of the mechanical vibrator 11, oscillate in electromagnetic cooperation with drive coil 29a and sensing coil 29b, as commonly known. Thus, oscillatory movement is transmitted from the arm 11b to feed pawl 12, thus the root end 12b thereof oscillating in the regular way, but the motion transmission through its pallet stone 12a to the ratchet wheel 13 being carried out substantially in the continuous way, as was referred to above.

The present embodiment provides a more stabilized motion-converting performance against outside me chanical shocks liable .to disturb the desired steady operation of the watch movement, especially by the additional provision of the second inertia wheel 24 in addition to the first inertia wheel 15 which corresponds to the flywheel mass 5.

The favorable antishock characteristic of the present embodiment of motion converter will be described more in detail hereinbelow:

When the watch movement is subjected to an outside disturbing shock, the movement and thus the motion converter will receive an acceleration. This acceleration can be divided into three Cartesian coordinate components, and a rotational torque. These Cartesian components will appear generally and substantially in the form of changes in the bearing frictions in all the rotational components of the gear train, yet including in this case the ratchet wheel 13. These frictional fluctuations will appear more specifically in the form of load fluctuations. Favorable performance in this respect was already analysed in the foregoing first embodiment, and same can be applied to the present embodiment.

Now turning to the problem of the disturbing turning torque and in the case of the present embodiment, however, under the assumption of dispensing with the second inertia wheel 24, such turning torque, when applied to the plate 25, will give rise to unintentional turngagement of the feed pawl with the ratchet teeth.

When the second inertia wheel 24 is provided so as to engage with the first inertia wheel 15, as was referred to above, for pfrforming opposite rotational movements to each other, the turning torques applied to these both inertia wheels are balanced out at their mutual engaging point, thus the relative relationship between the ratchet wheel and the plate is not modified and therefore preserved as before.

In the embodiment shown in FIG. 4, the moment of inertia of the first inertia wheel 15 is selected to be substantially equal to that of the second inertia wheel 24, as was referred to above. But, the invention is not limited only thereto. Both the inertia moments may be selected, if desired, so as to satisfy the following formula:

A n B where,

A stands for moment of inertia of wheel 15; B stands for moment of inertia of wheel 24; l n is the ratio of rotational speeds of the both wheels.

Even when such modification be employed, the same effect set forth above with reference to FIG. 4 can equally be attained. Thus, it can be said that for obtaining the above effect, it sufiic'es to select the moments of inertia of both the inertia wheels so that the algebraic sum of the angular momentums is nil. But, in the case of a clock movement where the rotational distur bance of the above kindis not liable to be encountered, there is no practical problem even if the second inertia wheel has been dispensed with, as in the case of the first embodiment.

For better understanding of the invention, an example of practical dimensions of the motion converter will be given by way of example of the second embodiment where the mechanical vibrator has been embodied into a tuning fork.

Number of vibrations of tuning fork 333% Hz; Length of tuning fork e 16 mm;

End masses on fork arms 2 X 0.5 g;

Amplitude as measured at tuning for end 70 p. (peak-topeak);

Amplitude as measured at the pivotal connection of feed pawl with tuning fork arm 25 p. (peak-to-peak); Number of teeth of ratchet wheel 225;

Outside diameter of ratchet wheel 3 mm.

The practical overall length (1,, plus 1 of feed pawl 12 was 7.3 mm; 1 2 mm; width: 2.] X mm; thickness: 2.4 X 10" mm; the moment of inertia of ratchet wheel 13 including first inertia wheel 15 was 2.67 X 10 g. cm; The included angle 0 was 90. Diameter of the movement amounted to about 30 mm.

According to our practical experiments, the aforementioned four assumptions, were found as substantially realized. The watch movement fitted with the present motion converter could operate in the stabilized condition, indeed, about one half of the conventionally encountered power. That was 13 volts; 4 A. Outside shocks or other conventionally encountered disturbing causes did not affect the regular movement of the watch.

In FIG. 5, several representative configurations of the axially resilient feed pawl constituting an important constituent of the motion converter are shown in somewhat schematically.

As was referred to hereinbefore, the first example of the feed pawl shown in FIG. 5a represents substantially that employed'in FIG. 4.

The second one shown in FIG. 5b is substantially that employed in FIG. 1. In this second example, the resilient portion 2b describes a zigzag wavy curve for providing the required resiliency and formed in the place in which the pawl 2 performs the necessary reciprocating and resiliently pivotal movement.

In the third example of feed pawl 42 shown in FIG. 50, the resilient portion 42b represents a zigzag wavy curve for providing the required resiliency and formed in the plane perpendicularto that in which the pawl performs the necessary reciprocating and resiliently pivotal movement.

In the fourth example of feed pawl 52 shown in FIG. 5d, the resilient portion 52b has a combined curve of the halves of the corresponding parts of the foregoing two examples shown in FIGS. 5b and 50.

In the fifth example of feed pawl 62 shown in FIG. 5e, the resilient portion 62b takes the form of a coil.

In the sixth example of feed pawl 72 shown in FIG. 5f, the resilient part 72b takes the form simply of a round open curve.

In the third example of feed pawl at 42, the root end proper thereof is shown as caught securely in a resilient open ring 42c which is adjustably pressed, on a stud pin, not shown, provided on the mechanical vibrator. This structural feature for fixingly mounting the root end of the feed pawl as was substantially described with reference to the first embodiment may be equally adopted, when necessary, in other examples of the feed pawl shown in FIGS. 5d, 5e and 5f although these root ends 52c, 62c and 72c are only shown schematically and in a highly simplified form. Palleted pawl ends 42a, 52a, 62a and 72a are each similar to that shown at 2a or 12a.

In the following at (I) and (II), it has been substantially demonstrated that the motion converter can operate in a stabilizing manner in the sense of automatic control technique. When analysed more specifically, the mechanism according to this invention may be stabilized when two or more ratchet teeth are fed per cycle of oscillation of the mechanical vibrator, with a certain different combination of several parameters P, K, f, n and A than that already mentioned hereinbefore. As an example, when a sudden outside mechanical shock is applied to the watch movement, a different mode of steady and stabilized operation of the motion converter could be brought about, wherein two teeth in place of one tooth of the ratchet wheel are fed per each oscillation of the vibrator. If the motion converter has been designed to feed a ratchet tooth per oscillation of the mechanical oscillator, the above mentioned phenomenon constitutes naturally a disturbing trouble for the regular time-keeping operation of the watch movement.

In the following, the mode of selection of these parameters for avoiding such operational trouble will be given.

Now assuming that the motion converter operates in its stabilized condition to feed n teeth per oscillation of the vibrator The conditions to be satisified are as follows:

i. when the ratchet wheel is rotating at a speed corresponding to a (n l) teeth per oscillation of the vibrator and when the amplitude of the feed pawl becomes its maximum allowable value (which may be expressed: A A then the maximum drive energy W (when X 0 E exerted by the oscillating pawl must be smaller whafw than the minimum load loss W,, for maintaining a (n l) teeth ratchet feed. Thus,

The prime in this case represents that the parameters relate to case (ii), while the doubled prime represents the aforementioned case (i). Under these conditions, the aforementioned parameter W will be obtained from formula (9).

WD"= F" V" dt m =nOKIfISD gWL Stabilized operation of the motion converter can be assured by selecting these parameters n, K, P, f and the like, so as to satisfy these equations (ll) and (12).

In F IG. 6, the two states (i) and (ii) are demonstrated as similar to FIG. 3.

With the motion converter according to this invention, it is also possible to feed one ratchet tooth for every m oscillations of the mechanical vibrator, when assuming that m is an integer of 2 or larger, and by selecting the ratchet tooth pitch somewhat larger than before. In this case, the regular ratchet tooth number per oscillation of the vibrator is (l /m) tooth, and in the case of an overdue tooth feed nearest to the regular tooth feed speed, it will amount to l )/(ml tooth per vibrator oscillation. Therefore, in this case, the formulae (11) and (12) will be:

then, from formula (10),

K e 2 g/mm Therefore, when the amplitude be 35 p. 44 u, the spring constant of feed pawl, ranging 2 2.5 g/mm will assure a stabilized operation of the motion converter for load loss: 7 I

1.45 [.LW, and a double pitched tooth feed of the ratchet can be effectively avoided.

As seen from the foregoing the motion converter according to this invention can provide a highly stabilized condition of the continuous time-keeping operation; one way self starting performance, and anti-shock performance in case of loadand amplitude fluctuations.

In addition, the following several advantages can easily be ascertained.

First, there is no operational uncertainty caused by occasional relative different position between feedand stop pawls, as conventionally encountered, since there is no stop pawl in the present motion converter. It should be further noted that the motion converter according to this invention is rather insensitive to occasional eccentric fabrication and/or mounting of the ratchet wheel, thus otherwise necessary mounting adjustment can be substantially dispensed with and thereby a substantially decreased manufacturing cost as well as increased assembly job is assured. A further possibility is such that substantially finer ratchet teeth rotation of the ratchet wheel. Although occasional reverse rotation of ratchet wheel could occur when the load is exceptionally large and the equivalent inertia of the ratchet wheel is rather small, the stop motion can completely be avoided.

Occasional fluctuation of the kinetic energy owned by the rotating ratchet wheel is always consumed within the system of the time-keeping gear train. Ineffective energy consumption by the collision of the ratchet tooth with the feed pawl pallet has been completely avoided. These features are highly advantageous for adopting a high frequency vibrator or in the fitting of the motion converter in a larger size timepiece, if necessary.

Since the feed pawl has a substantial resiliency in its oscillating direction, a soft and resilient contact will be maintained in case where a sudden and substantial outside shock is applied to the timepiece movement.

It will be further seen from the foregoing that the invention is not limited-to the aforementioned specific embodiment. One feature adopted in one of the embodiment can be adopted in another, so far as there be no conflict. In a modification, the feed pawl can be fabricated into a substantially straight one, the spring portion being provided in close proximity of the root end of the feed pawl. The vibrator can be formed into any one of the conventional designs.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A timepiece motion converter mechanism comprising an oscillatable mechanical vibrator, a rotatable ratchet wheel having a plurality of teeth on the circumference thereof, a feed pawl secured at its root end to said vibrator with the free end thereof disposed in cooperative engagement with said ratchet teeth, said feed pawl having resilient means to provide substantial resiliency in the oscillating direction of said pawl, and inertia means operably connected to said ratchet wheel to provide a substantial moment of inertia whereby said pawl resiliency and said moment of inertia cooperate to provide a substantially continuous and constant rotation of said ratchet wheel.

2. A motion converter as set forth in claim 1 wherein said inertia means is comprised of a first inertia wheel secured to said ratchet wheel for rotation therewith to provide said substantial moment of inertia.

3. A motion converter as set forth in claim 2 further comprising a second inertia wheel and gear means interconnecting said first inertia wheel with said second 14 inertia wheel to provide the necessary substantial moment of inertia to said ratchet wheel.

4. A motion converter as set forth in claim 3 wherein the angular momentum of said first inertia wheel is substantially equal to that of the second inertia wheel.

5. A motion converter as set forth in claim 1 wherein said ratchet wheel is operatively connected with a timekeeping and time-indicating gear train comprising a series of intermeshing gears; the sum of the absolute values of angular momentum of said ratchet wheel and the constituent gears of said gear train which rotate in the same direction as that of said ratchet wheel being substantially equal to the sum of the absolute values of angular momentum of the remaining gears of said gear train which rotate in the opposite direction to that of said ratchet wheel. 

1. A timepiece motion converter mechanism comprising an oscillatable mechanical vibrator, a rotatable ratchet wheel having a plurality of teeth on the circumference thereof, a feed pawl secured at its root end to said vibrator with the free end thereof disposed in cooperative engagement with said ratchet teeth, said feed pawl having resilient means to provide substantial resiliency in the oscillating direction of said pawl, and inertia means operably connected to said ratchet wheel to provide a substantial moment of inertia whereby said pawl resiliency and said moment of inertia cooperate to provide a substantially continuous and constant rotation of said ratchet wheel.
 2. A motion converter as set forth in claim 1 wherein said inertia means is comprised of a first inertia wheel secured to said ratchet wheel for rotation therewith to provide said substantial moment of inertia.
 3. A motion converter as set forth in claim 2 further comprising a second inertia wheel and gear means interconnecting said first inertia wheel with said second inertia wheel to provide the necessary substantial moment of inertia to said ratchet wheel.
 4. A motion converter as set forth in claim 3 wherein the angular momentum of said first inertia wheel is substantially equal to that of the second inertia wheel.
 5. A motion converter as set forth in claim 1 wherein said ratchet wheel is operatively connected with a time-keeping and time-indicating gear train comprising a series of intermeshing gears; the sum of the absolute values of angular momentum of said ratchet wheel and the constituent gears of said gear train which rotate in the same direction as that of said ratchet wheel being substantially equal to the sum of the absolute values of angular momentum of the remaining gears of said gear train which rotate in the opposite direction to that of said ratchet wheel. 